Color conversion helpers, see also fiee/fiee-coloree

colors.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

def HtmlColorCode_to_strings(value):
    "Convert a HTML color code like '#FFCC00' or 'FFCC00' to a list of strings ['FF', 'CC', '00']"
    x = 1 * value.startswith('#')
    return [value[x:x+2],value[x+2:x+4],value[x+4:x+6]]
        
def HtmlColorCode_to_ints(value):
    "Convert a HTML color code like '#FFCC00' or 'FFCC00' to a list of integers [255, 204, 0]"
    return [int(x, 16) for x in HtmlColorCode_to_strings(value)]
        
def HtmlColorCode_to_floats(value):
    "Convert a HTML color code like '#FFCC00' or 'FFCC00' to a list of floats [1.0, 0.8, 0.0]"
    #return (float.fromhex('0x'+x)/255 for x in HtmlColorCode_to_strings(value))
    # fromhex is python 2.6, rest works with 2.5!
    return [float(int(x, 16))/255 for x in HtmlColorCode_to_strings(value)]

def RGB_to_CMYK(r, g, b, ucr=1.0):
    """
    Take r,g,b float values (0.0 to 1.0), 
    invert to get c,m,y, 
    apply UCR (0.0 to 1.0; 0 means no UCR = CMY separation), 
    return c,m,y,k as integers (percent values)
    
    This is a simple number conversion that ignores the basics of color management (no profiles involved)!
    """
    c,m,y = (1.0 - (float(x)/2) for x in (g+b, r+b, r+g))
    k = min(c,m,y)*ucr
    c,m,y = c-k, m-k, y-k
    return [int(round(x*100)) for x in (c,m,y,k)]

def HtmlColorCode_to_CMYK(value, ucr=1.0):
    """
    Convert a HTML color code like '#FFCC00' or 'FFCC00' to a list of integers (CMYK percent values)
    """
    (r,g,b) = HtmlColorCode_to_floats(value)
    return RGB_to_CMYK(r,g,b,ucr)

def CMYK_to_RGB(cmyk):
    """
    Convert a comma separated integer list into RGB float values, i.e.
    '100,80,0,0' to (0.0, 51.0, 255.0)
    Returns None for invalid input.
    
    This is a simple number conversion that ignores the basics of color management (no profiles involved)!
    """
    c,m,y,k = (float(x) for x in cmyk.split(','))
    
    if max(c+k, m+k, y+k) > 100:
        k = 100 - max(c,m,y)
    return [(1 - (x+k)/100)*255 for x in (c,m,y)]

def CMYK_to_HtmlColorCode(cmyk):
    """
    Convert a comma separated integer list into a HTML hex color code, i.e.
    '100,80,0,0' to '#0032FF'
    Returns empty string for invalid input.
    
    This is a simple number conversion that ignores the basics of color management (no profiles involved)!
    """
    t = CMYK_to_RGB(cmyk)
    if t: return '#%02X%02X%02X' % (t[0], t[1], t[2])
    return ''

def color_spot(htmlcolorcode, text=None):
    """
    HTML snippet: span with class 'colorspot' and `htmlcolorcode` as background color
    """
    if text is None:
        text = htmlcolorcode
    return u'<span class="colorspot" style="background-color:%s;">&nbsp;&nbsp;&nbsp;</span> %s' % (htmlcolorcode, text)